Motion control systems typically utilize variable resistive devices, such as potentiometers or linear strip variable resistors, as low-cost, absolute position feedback sensors. Accurate motion control is critical in many system applications, especially in medical imaging systems such as SPECT, PET and MRI imaging systems where accurate positioning of movable components such as patient beds, gantries, detector heads, etc. is essential.
One disadvantage in the use of such variable resistive position sensors is that the electro-mechanical contact of such device can experience an intermittent or permanent failure. While a permanent failure is readily apparent, the susceptibility of specific resistive feedback sensors to intermittent failures can be difficult to identify when equipment is serviced because the failure may not occur during a service inspection. For example, where a contact is prone to intermittent failure due to a contaminant such as dirt or debris, or gradual deterioration of the contact material, movement of the variable resistive device could affect a temporary cleaning of the electro-mechanical contact and thus preclude detection of the underlying problem during servicing of the system. Accordingly, it would be desirable to have the capability of detecting intermittent failures of resistive feedback devices.